parse klp backport properties from livepatch.h

Avoid further cluttering of kpatch-build by per-distro
exceptions to the usual inference from KERNEL_VERSION of
core klp properties NO_KLP_ARCH or HAVE_KLP_REPLACE.

Rather than tweak kpatch-build to reflect each distro's
different backporting of livepatch core code from upstream,
at each reported KERNEL_VERSION, advertise in <linux/livepatch.h>
those kernel properties that have been backported from upstream,
overriding the logic based on KERNEL_VERSION as needed.

Signed-off-by: Pete Swain <swine@google.com>

Author: swine

kpatch-build/kpatch-build

@@ -224,6 +224,8 @@ use_klp_arch()
 {
 	if kernel_is_rhel; then
 		! rhel_kernel_version_gte 4.18.0-284.el8
+	elif egrep -sq '^#define\s*NO_KLP_ARCH' include/linux/livepatch.h; then
+		false # kernel needs no .klp.arch sections
 	else
 		! kernel_version_gte 5.8.0
 	fi
@@ -233,6 +235,8 @@ support_klp_replace()
 {
 	if kernel_is_rhel; then
 		rhel_kernel_version_gte 4.18.0-193.el8
+	elif egrep -sq '^#define\s*HAVE_KLP_REPLACE' include/linux/livepatch.h; then
+		true # kernel explicitly indicates support
 	else
 		kernel_version_gte 5.1.0
 	fi

test/integration/kpatch-test

@@ -317,6 +317,8 @@ support_klp_replace()
 {
 	if kernel_is_rhel; then
 		rhel_kernel_version_gte 4.18.0-193.el8
+	elif egrep -sq '^#define\s*HAVE_KLP_REPLACE' include/linux/livepatch.h: then
+		true # kernel explicitly indicates support
 	else
 		kernel_version_gte 5.1.0
 	fi